"""
Author  : Turfa Auliarachman
Date    : October 12, 2016

This is a pure Python implementation of Dynamic Programming solution to the edit distance problem.

The problem is :
Given two strings A and B. Find the minimum number of operations to string B such that A = B. The permitted operations are removal,  insertion, and substitution.
"""
from __future__ import print_function


class EditDistance:
    """
    Use :
    solver              = EditDistance()
    editDistanceResult  = solver.solve(firstString, secondString)
    """

    def __init__(self):
        self.__prepare__()

    def __prepare__(self, N=0, M=0):
        self.dp = [[-1 for y in range(0, M)] for x in range(0, N)]

    def __solveDP(self, x, y):
        if (x == -1):
            return y + 1
        elif (y == -1):
            return x + 1
        elif (self.dp[x][y] > -1):
            return self.dp[x][y]
        else:
            if (self.A[x] == self.B[y]):
                self.dp[x][y] = self.__solveDP(x - 1, y - 1)
            else:
                self.dp[x][y] = 1 + min(self.__solveDP(x, y - 1), self.__solveDP(x - 1, y), self.__solveDP(x - 1, y - 1))

            return self.dp[x][y]

    def solve(self, A, B):
        if isinstance(A, bytes):
            A = A.decode('ascii')

        if isinstance(B, bytes):
            B = B.decode('ascii')

        self.A = str(A)
        self.B = str(B)

        self.__prepare__(len(A), len(B))

        return self.__solveDP(len(A) - 1, len(B) - 1)


if __name__ == '__main__':
    try:
        raw_input  # Python 2
    except NameError:
        raw_input = input  # Python 3

    solver = EditDistance()

    print("****************** Testing Edit Distance DP Algorithm ******************")
    print()

    print("Enter the first string: ", end="")
    S1 = raw_input().strip()

    print("Enter the second string: ", end="")
    S2 = raw_input().strip()

    print()
    print("The minimum Edit Distance is: %d" % (solver.solve(S1, S2)))
    print()
    print("*************** End of Testing Edit Distance DP Algorithm ***************")
